# If $\alpha=\large\frac{5}{2 ! 3}+\frac{5.7}{3 ! 3^2}+ \frac{5.7.9}{4 ! 3^3}+........,$ then $\alpha^2+4 \alpha=$

$\begin {array} {1 1} (1)\;21 & \quad (2)\;23 \\ (3)\;25 & \quad (4)\;27 \end {array}$

(2) 23
answered Nov 7, 2013 by
Can u plz explain the steps